Figure 2: Map of the Za Hajovnou cave (modified after Musil,
2014; Lundberg et al., 2014; Kadlec et al., 2014). Locations marked by
“Section No. 1” and “Section No. 2” is discussed in the text (Kadlec
et al., 2005, 2014). Map shows relation between Connecting Passage
Corridor, Birthday Corridor, and Excavated Corridor (m a.s.l.: meter
above sea level).
Upper sediments of the cave were dated by U/Th dating of flowstones to
118 ± 1 to 267 ± 3 ka and by inferred Matuyama-Brunhes boundary in
Section No. 1 (Figure 3) (Musil, 2005; Kadlec et al., 2005, 2014;
Lundberg et al., 2014; Babek et al 2015). The sedimentation in the cave
corridors were active probably from the Early Pleistocene until the
beginning of the Middle Pleistocene. The sediment then consists of
Pleistocene glacial time in north-western Europe called Cromerian
Interglacials complex (Muller, 1992), MIS19 (marine isotope stage) which
is interglacial period ~780 ka (Pol et al., 2019) and
Matuyama-Brunhes reversal (Kadlec et al. 2005, 2014; Musil et al., 2014;
Musil, 2014; Zak et al., 2018; Lundberg et al., 2014).
The Matuyama-Brunhes boundary (781 ka) was suggested in the upper part
of the backwater fine sediments, deposited from suspension in the
flooded cave. These sediments underlay the mostly non-fluvial deposits
which entered the cave through a steep passage and filled the Connecting
Passage Corridor. (Kadlec et al., 2014; Lundberg et al., 2014; Musil et
al., 2014).
Sedimentary sections retrieved in the Za Hajovnou cave by Kadlec et al.
(2005, 2014) were composed of two parts. The first part (Section No. 1,
in Figure 2) was situated in the Excavated Corridor about 28 m from the
cave entrance (Kadlec et al., 2005) (Figure 2). It was intepretted to
contain the magnetic transition from a reversed to a normal polarity and
inferred from the age dates of the overlying non- fluvial sediments,
that it could be the Matuyama-Brunhes reversal (Kadlec et al., 2005).
The second sedimentary section (Section No. 2) partially overlapped the
Section No. 1, and was located in the Excavated Corridor (Kadlec et al.,
2014) (Figure 2). Kadlec et al. (2014) indicated that this section had
sediment with just reversed polarity except upper part of the sediment
where the magnetization was difficult to interpret because the sediments
had weak magnetization for which the sensitivity of the Agico JR-6A
spinner magnetomer was insufficient. Section No. 2 underlies the Section
No. 1 and contained older backwater sediment with reversed magnetic
polarity (age > 781 ka, (Kadlec et al., 2014)).
The difficulties in interpretation of the primary study by Kadlec et al.
(2014) was the motivation for the presented research. Here we collected
44 oriented discrete sedimentary samples from the Excavated Corridor
near the upper backwater sedimentary Section No. 1 (Figure 2, 3).